1. Field of Invention
The present invention relates generally to a modem having detection circuitry for particular telephone communication line events, and specifically to a system and method for detecting telephone line-in-use, extension pick-up, and remote hang-up in a modem.
2. Background of the Invention
Modem communication over telephone communication lines has gained widespread usage with the growing number of multi-media applications implemented using personal computers. Personal computers (PCs) now perform many different types of data transfers over telephone communication lines, such as accessing the "Internet," communicating data files between PCs, sending and receiving facsimiles, and acting as an answering machine by sending and receiving voice information over the telephone communication lines. Modems are used to convert between a computer's digital signals and analog signals that can be carried on the telephone network's analog transmission lines.
In using a conventional modem to interface a telephone communication line for such data transfers, there are several telephone communication line conditions that can adversely affect the performance of the modem and/or the telephone connection. For instance, in households having multiple telephone extensions connected to a single telephone communication line, it is possible for a person to try to establish a modem connection with the telephone communication line while another person in the household is already talking over the telephone communication line using another telephone extension. If the telephone communication line is already in use, the person on the telephone will hear annoying "popping" sounds generated by the modem trying to go off-hook in order to dial out. Moreover, most modems are configured to repeatedly reattempt to seek a dial tone to thereby enter the off-hook mode after failed previous attempts. This results in the annoying "popping" sounds being periodically heard by the persons speaking on the telephone while the modem attempts to dial out.
When a conventional modem is used in connection with performing answering machine functions, several difficulties may arise. Once the modem receives an incoming telephone call and enters an answering machine mode, such as commencing with its outgoing message or recording an incoming message, it is possible for a person to pick-up the telephone extension during the progression of the answering machine mode. This may often occur when a person hears an incoming phone call but is not able to pick-up the telephone extension until after the modem has already initiated the answering machine mode.
Most conventional modems communicate by negotiating commands between the calling and receiving modems. Once the calling modem has completed its transmission, the calling modem typically sends a command to the receiving modem indicating that the transmission is complete. The receiving modem then knows to go on-hook (hang-up). However, when receiving voice information while operating in an answering machine mode, modems will not receive such commands over the telephone communication line indicating that the voice message has been completed.
Additionally, the advent of multi-line modems has increased the problems associated with dual use of a telephone communication line. A single computing device may employ a multi-line modem, or a number of single line modems working in parallel, to increase the bandwidth of a connection, to negotiate parallel communications with multiple partners, or both. When another telephony device attached to a telephone communication line that the multi-line computing device is using goes off hook, a user must manually disable the connection on that telephone communication line to allow the use of the other connected telephony device. Additionally, when the telephony device connected to such a telephone communication line goes on hook and frees up a telephone communication line, the user also must enable the telephone communication line to the computing device manually.